Commercial transport aircraft are typically designed to carry a given load of passengers, cargo, or passengers and cargo over a given range. Occasionally, however, the need arises to change the role of the aircraft. For example, some commercial transport aircraft may be converted to aerial refueling tankers and/or receiver aircraft (i.e., the aircraft to be refueled). Although in-flight refueling (or air-to-air refueling) is a relatively common operation, especially for military aircraft, the conversion of a commercial transport aircraft to include in-flight refueling capabilities includes converting a number of aircraft systems. One such system that must be converted is the fuel system.
Modern aircraft include complex fuel systems that route aviation fuel from fuel tanks to aircraft systems that use the fuel. These aircraft systems can include the primary engines and/or auxiliary power units (APUs). In the case of an aerial refueling tanker and/or receiver aircraft, these systems can also include the fluid conduits (e.g., fuel lines), manifolds, and associated valving necessary for delivering fuel to a receiver aircraft and/or receiving fuel in-flight from a tanker aircraft. In a receiver aircraft, for example, the fuel lines pass from a forward portion of the aircraft (where the fuel is received from the tanker aircraft), through at least a portion of the fuselage, and into one or more fuel tanks of the receiver aircraft. Furthermore, the fuel lines may pass through “ignition zones,” which are typically pressurized compartments in the aircraft (e.g., baggage compartments) that may also house electrical devices.
One concern with this arrangement is that the fuel passing through the fluid conduits imparts substantial loads on the fluid conduits and other structures of the aircraft that were not designed for such loads, particularly in the case of converted aircraft. Accordingly, there is a need to transfer the imposed loads from the fluid conduits to the appropriate reaction locations of the aircraft. The loads must be transferred (a) in accordance with various loading conditions imposed by regulatory agencies, (b) without venting hazardous fuels in an undesired area, and (c) without violating Federal Aviation Administration (FAA) regulations requiring accessible and shrouded fuel lines.